Adaptive framework for closed-loop protocols over photonic burst switched networks

ABSTRACT

An optical network, which includes edge and switching nodes, optically communicate information formatted into statistically multiplexed control and data bursts and/or metadata. Control bursts are transmitted prior to the data bursts to configure optical switches in selected switching nodes so that the data bursts do not require O-E-O conversion. Each edge node consists of an adaptive PBS medium-access layer (MAC) component in order to achieve the transmission throughput improvement. The adaptive PBS MAC component enables the PBS data burst size to adapt to the TCP flow, allowing the PBS data burst to be transmitted immediately for the TCP flow experiencing TCP slow start. It performs a “deep” packet inspection of control packets coming back to the data source from the destination PBS network edge node to detect packet losses.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application is related to U.S. patent application Ser. No. 10/126,091, filed Apr. 17, 2002; U.S. patent application Ser. No. 10/183,111, filed Jun. 25, 2002; U.S. patent application Ser. No. 10/328,571, filed Dec. 24, 2002; U.S. patent application Ser. No. 10/377,312 filed Feb. 28, 2003; U.S. patent application Ser. No. 10/377,580 filed Feb. 28, 2003; U.S. patent application Ser. No. 10/417,823 filed Apr. 16, 2003; U.S. patent application Ser. No. 10/417,487 filed Apr. 17, 2003; and U.S. patent application Ser. No. (Attorney Docket No. 42P16183) filed May 19, 2003.

FIELD OF THE INVENTION

[0002] An embodiment of the present invention relates to optical networks in general; and, more specifically, to signaling of control and data bursts within optical switched networks.

BACKGROUND INFORMATION

[0003] Transmission bandwidth demands in telecommunication networks (e.g., the Internet) appear to be ever increasing and solutions are being sought to support this bandwidth demand. One solution to this problem is to use fiber-optic networks, where wavelength-division-multiplexing (WDM) technology is used to support the ever-growing demand in optical networks for higher data rates.

[0004] Conventional optical switched networks typically use wavelength routing techniques, which require that optical-electrical-optical (O-E-O) conversion of optical signals be done at the optical switches. O-E-O conversion at each switching node in the optical network is not only very slow operation (typically about ten milliseconds), but it is very costly, and potentially creates a traffic bottleneck for the optical switched network. In addition, the current optical switch technologies cannot efficiently support “bursty” traffic that is often experienced in packet communication applications (e.g., the Internet).

[0005] A large communication network can be implemented using several sub-networks. For example, a large network to support Internet traffic can be divided into a large number of relatively small access networks operated by Internet service providers (ISPs), which are coupled to a number of metropolitan area networks (Optical MANs), which are in turn coupled to a large “backbone” wide area network (WAN). The optical MANs and WANs typically require a higher bandwidth than local-area networks (LANs) in order to provide an adequate level of service demanded by their high-end users. However, as LAN speeds/bandwidth increase with improved technology, there is a need for increasing MAN/WAN speeds/bandwidth.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

[0007]FIG. 1 is a simplified block diagram illustrating a photonic burst-switched (PBS) network, according to one embodiment of the present invention.

[0008]FIG. 2 is a simplified flow diagram illustrating the operation of a photonic burst-switched (PBS) network, according to one embodiment of the present invention.

[0009]FIG. 3 is a block diagram illustrating a switching node module for use in a photonic burst-switched (PBS) network, according to one embodiment of the present invention.

[0010]FIGS. 4A and 4B are diagram illustrating the format of an optical data burst and an optical control burst for use in a photonic burst-switched (PBS) network, according to one embodiment of the present invention.

[0011]FIG. 5 is a flow diagram illustrating the operation of a switching node module, according to one embodiment of the present invention.

[0012]FIG. 6 is a diagram illustrating a generalized multi-protocol label switching (GMPLS)-based architecture for a PBS network, according to one embodiment of the present invention.

[0013]FIG. 7 is a diagram illustrating PBS optical burst flow between edge nodes and a switching node in a PBS network, according to one embodiment of the present invention.

[0014]FIG. 8 is a diagram illustrating a PBS framing format for PBS optical bursts, according to one embodiment of the present invention.

[0015]FIG. 9 is a block diagram illustrating an edge node with adaptive monitoring for use in a PBS network, according to one embodiment of the present invention.

[0016]FIG. 10 is a flow diagram illustrating the operation of an edge node during ingress adaptive monitoring, according to one embodiment of the present invention.

[0017]FIG. 11 is a flow diagram illustrating the operation of an edge node during egress adaptive monitoring, according to one embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0018]FIG. 1 illustrates a photonic burst-switched (PBS) network 10, according to one embodiment of the present invention. The term photonic burst is used herein to refer to statistically multiplexed packets (e.g., Internet protocol (IP) packets or Ethernet frames) having similar routing requirements). A photonic burst typically includes a photonic label including the header and other routing information of the IP packets and a payload including the data segments of the packets.

[0019] This embodiment of PBS network 10 is connected to external networks such as local area networks (LANs) 13 ₁-13 _(N) and a backbone optical WAN (not shown). In addition, this embodiment of PBS network 10 includes ingress nodes 15 ₁-15 _(M), switching nodes 17 ₁-17 _(L), and egress nodes 18 ₁-18 _(K). PBS network 10 can include other ingress, egress and switching nodes (not shown) that are interconnected with the switching nodes shown in FIG. 1. The ingress and egress nodes are also referred to herein as edge nodes in that they logically reside at the edge of the PBS network. The edge nodes, in effect, provide an interface between the aforementioned “external” networks (i.e., external to the PBS network) and the switching nodes of the PBS network. In this embodiment, the ingress, egress and switching nodes are implemented with intelligent modules. This embodiment can be used, for example, as a metropolitan area network connecting a large number of LANs within the metropolitan area to a large optical backbone network.

[0020] In some embodiments, the ingress nodes perform optical-electrical (O-E) conversion of received optical signals, and include electronic memory to buffer the received signals until they are sent to the appropriate LAN. In addition, in some embodiments, the ingress nodes also perform electrical-optical (E-O) conversion of the received electrical signals before they are transmitted to switching nodes 17 ₁-17 _(M) of PBS network 10.

[0021] Egress nodes are implemented with optical switching units or modules that are configured to receive optical signals from other nodes of PBS network 10 and route them to the optical WAN or other external networks. Egress nodes can also receive optical signals from the optical WAN or other external network and send them to the appropriate node of PBS network 10. In one embodiment, egress node 18 ₁ performs O-E-O conversion of received optical signals, and includes electronic memory to buffer received signals until they are sent to the appropriate node of PBS network 10 (or to the optical WAN).

[0022] Switching nodes 17 ₁-17 _(L) are implemented with optical switching units or modules that are each configured to receive optical signals from other switching nodes and appropriately route the received optical signals to other switching nodes of PBS network 10. As is described below, the switching nodes perform O-E-O conversion of optical control bursts and network management control burst signals. In some embodiments, these optical control bursts and network management control bursts are propagated only on preselected wavelengths. The preselected wavelengths do not propagate optical “data” bursts (as opposed to control bursts and network management control bursts) signals in such embodiments, even though the control bursts and network management control bursts may include necessary information for a particular group of optical data burst signals. The control and data burst information is transmitted on separate wavelengths in some embodiments, which is also referred to herein as out-of-band (OOB) signaling. In other embodiments, control and data information may be sent on the same wavelengths (also referred to herein as in-band signaling). In another embodiment, optical control bursts, network management control bursts, and optical data burst signals may be propagated on the same wavelength(s) using different encoding schemes such as different modulation formats, etc. In either approach, the optical control bursts and network management control bursts are sent asynchronously relative to its corresponding optical data burst signals. In still another embodiment, the optical control bursts and other control signals are propagated at different transmission rates as the optical data signals.

[0023] Although switching nodes 17 ₁-17 _(L) may perform O-E-O conversion of the optical control signals, in this embodiment, the switching nodes do not perform O-E-O conversion of the optical data burst signals. Rather, switching nodes 17 ₁-17 _(L) perform purely optical switching of the optical data burst signals. Thus, the switching nodes can include electronic circuitry to store and process the incoming optical control bursts and network management control bursts that were converted to an electronic form and use this information to configure photonic burst switch settings, and to properly route the optical data burst signals corresponding to the optical control bursts. The new control bursts, which replace the previous control bursts based on the new routing information, are converted to an optical control signal, and it is transmitted to the next switching or egress nodes. Embodiments of the switching nodes are described further below.

[0024] Elements of exemplary PBS network 10 are interconnected as follows. LANs 13 ₁-13 _(N) (external of PBS network 10) are connected to corresponding ones of ingress nodes 15 ₁-15 _(M) of PBS network 10. Within PBS network 10, ingress nodes 15 ₁-15 _(M) and egress nodes 18 ₁-18 _(K) are connected to some of switching nodes 17 ₁-17 _(L) via optical fibers. Switching nodes 17 ₁-17 _(L) are also interconnected to each other via optical fibers in mesh architecture to form a relatively large number of lightpaths or optical links between the ingress nodes, and between ingress nodes 15 ₁-15 _(L) and egress nodes 18 ₁-18 _(K). Ideally, there are more than one lightpath to connect the switching nodes 17 ₁-17 _(L) to each of the endpoints of PBS network 10 (i.e., the ingress nodes and egress nodes are endpoints within PBS network 10). Multiple lightpaths between switching nodes, ingress nodes, and egress nodes enable protection switching when one or more node fails, or can enable features such as primary and secondary route to destination.

[0025] As described below in conjunction with FIG. 2, the ingress, egress and switching nodes of PBS network 10 are configured to send and/or receive optical control bursts, optical data burst, and other control signals that are wavelength multiplexed so as to propagate the optical control bursts and control labels on pre-selected wavelength(s) and optical data burst or payloads on different preselected wavelength(s). Still further, the edge nodes of PBS network 10 can send optical control burst signals while sending data out of PBS network 10 (either optical or electrical).

[0026]FIG. 2 illustrates the operational flow of PBS network 10, according to one embodiment of the present invention. Referring to FIGS. 1 and 2, photonic burst switching network 10 operates as follows.

[0027] PBS network 10 receives packets from LANs 13 ₁-13 ₁N. In one embodiment, PBS network 10 receives IP packets at ingress nodes 15 ₁-15 _(M). The received packets can be in electronic form rather than in optical form, or received in optical form and then converted to electronic form. In this embodiment, the ingress nodes store the received packets electronically. A block 20 represents this operation.

[0028] For clarity, the rest of the description of the operational flow of PBS network 10 focuses on the transport of information from ingress node 15 ₁ to egress node 181. The transport of information from ingress nodes 15 ₂-15 _(M) to egress node 18, (or other egress nodes) is substantially similar.

[0029] An optical burst label (i.e., an optical control burst) and optical payload (i.e., an optical data burst) is formed from the received packets. In one embodiment, ingress node 15 ₁ uses statistical multiplexing techniques to form the optical data burst from the received IP (Internet Protocol) packets stored in ingress node 15 ₁. For example, packets received by ingress node 15 ₁ and having to pass through egress node 18 ₁ on their paths to a destination can be assembled into an optical data burst payload. Statistical multiplexing generally refers to techniques for sharing a link or channel by multiple data sources based on statistics of the bandwidth used by the sources (e.g., an average) rather than the peak bandwidth required by each source. For example, statistical multiplexing techniques are disclosed by K. Kumaran and M. Mandjes, “Multiplexing Regulated Traffic Streams: Design and Performance” in Proc. of IEEE INFOCOM 2001; C.-F. Su and G. de Veciana, “On Statistical Multiplexing, Traffic Mixes, and VP Management” in Proc. of IEEE INFOCOM 1998; B. Maglaris, D. Anastassiou, P. Sen, G. Karlsson, and J. D. Robbins, “Performance Models of Statistical Multiplexing in Packet Video Communications,” IEEE Transaction on Communications 36, 834-844, 1988, T. Brown, “Adaptive Statistical Multiplexing For Broadband Communication”, Chapter 3, of “Performance Evaluation and Application of ATM Networks”, Kouvatsos, D. editor, Kluwer, 2000. Other embodiments can use any suitable statistical multiplexing technique. A block 21 represents this operation.

[0030] Bandwidth on a specific optical channel and/or fiber is reserved to transport the optical data burst through PBS network 10. In one embodiment, ingress node 15 ₁ reserves a time slot (i.e., a time slot of a TDM system) in an optical data signal path through PBS network 10. This time slot maybe fixed-time duration and/or variable-time duration with either uniform or non-uniform timing gaps between adjacent time slots. Further, in one embodiment, the bandwidth is reserved for a time period sufficient to transport the optical burst from the ingress node to the egress node. For example, in some embodiments, the ingress, egress, and switching nodes maintain an updated list of all used and available time slots. The time slots can be allocated and distributed over multiple wavelengths and optical fibers. Thus, a reserved time slot (also referred to herein as a TDM channel), that in different embodiments may be of fixed-duration or variable-duration, may be in one wavelength of one fiber, and/or can be spread across multiple wavelengths and multiple optical fibers. A block 22 represents this operation.

[0031] When an ingress and/or egress node reserves bandwidth or when bandwidth is released after an optical data burst is transported, a network controller (not shown) updates the list. In one embodiment, the network controller and the ingress or egress nodes perform this updating process using various burst or packet scheduling algorithms based on the available network resources and traffic patterns. The available variable-duration TDM channels, which are periodically broadcasted to all the ingress, switching, and egress nodes, are transmitted on the same wavelength as the optical control bursts or on a different common preselected wavelength throughout the optical network. The network controller function can reside in one of the ingress or egress nodes, or can be distributed across two or more ingress and/or egress nodes. In this embodiment, the network controller is part of control unit 37 (FIG. 3), which can include one or more processors.

[0032] The optical control bursts, network management control labels, and optical data bursts are then transported through photonic burst switched network 10 in the reserved time slot or TDM channel. In one embodiment, ingress node 15 ₁ transmits the control burst to the next node along the optical label-switched path (OLSP) determined by the network controller. In this embodiment, the network controller uses a constraint-based routing protocol [e.g., generalized multi-protocol label switching (GMPLS) Draft Internet Engineering Task Force (IETF) Architecture-05 Internet-Draft, March 2003] over one or more wavelengths to determine the best available OLSP to the egress node.

[0033] In one embodiment, the control label (also referred to herein as a control burst) is transmitted asynchronously ahead of the photonic data burst and on a different wavelength and/or different fiber. The time offset between the control burst and the data burst allows each of the switching nodes to process the label and configure the photonic burst switches to appropriately switch before the arrival of the corresponding data burst. The term photonic burst switch is used herein to refer to fast optical switches that do not use O-E-O conversion.

[0034] In one embodiment, ingress node 15 ₁ then asynchronously transmits the optical data bursts to the switching nodes where the optical data bursts experience little or no time delay and no O-E-O conversion within each of the switching nodes. The optical control burst is always sent before the corresponding optical data burst is transmitted.

[0035] In some embodiments, the switching node may perform O-E-O conversion of the control bursts so that the node can extract and process the routing information included in the label. Further, in some embodiments, the TDM channel is propagated in the same wavelengths that are used for propagating labels. Alternatively, the labels and payloads can be modulated on the same wavelength in the same optical fiber using different modulation formats. For example, optical labels can be transmitted using non-return-to-zero (NRZ) modulation format, while optical payloads are transmitted using return-to-zero (RZ) modulation format. The optical burst is transmitted from one switching node to another switching node in a similar manner until the optical control and data bursts are terminated at egress node 18 ₁. A block 23 represents this operation.

[0036] The operational flow at this point depends on whether the target network is an optical WAN or a LAN. A block 24 represents this branch in the operational flow.

[0037] If the target network is an optical WAN, new optical label and payload signals are formed. In this embodiment, egress node 18 ₁ prepares the new optical label and payload signals. A block 25 represents this operation.

[0038] The new optical label and payload are then transmitted to the target network (i.e., WAN in this case). In this embodiment, egress node 18 ₁ includes an optical interface to transmit the optical label and payload to the optical WAN. A block 26 represents this operation.

[0039] However, if in block 24 the target network is a LAN, the optical data burst is disassembled to extract the IP packets or Ethernet frames. In this embodiment, egress node 18 ₁ converts the optical data burst to electronic signals that egress node 18 ₁ can process to recover the data segment of each of the packets, as represented in block 27.

[0040] The extracted IP data packets or Ethernet frames are processed, combined with the corresponding IP labels, and then routed to the target network (i.e., LAN in this case). In this embodiment, egress node 18 ₁ forms these new IP packets. A block 28 represents this operation. The new IP packets are then transmitted to the target network (i.e., LAN) as represented in block 29.

[0041] PBS network 10 can achieve increased bandwidth efficiency through the additional flexibility afforded by the TDM channels. Although this exemplary embodiment described above includes an optical MAN having ingress, switching and egress nodes to couple multiple LANs to an optical WAN backbone, in other embodiments the networks do not have to be LANs, optical MANs or WAN backbones. That is, PBS network 10 may include a number of relatively small networks that are coupled to a relatively larger network that in turn is coupled to a backbone network.

[0042] Although a WDM embodiment is described above, in other embodiments, a single wavelength can be used for the entire PBS network. Some of these single wavelength alternative embodiments have multiple optical fibers interconnections between each node to provide increased bandwidth.

[0043]FIG. 3 illustrates a module 17 for use as a switching node in photonic burst switched network 10 (FIG. 1), according to one embodiment of the present invention. In this embodiment, module 17 includes a set of optical wavelength division demultiplexers 30 ₁-30 _(A), where A represents the number of input optical fibers used for propagating payloads, labels, and other network resources to the module. For example, in this embodiment, each input fiber could carry a set of C wavelengths (i.e., WDM wavelengths), although in other embodiments the input optical fibers may carry differing numbers of wavelengths. Module 17 would also include a set of N×N photonic burst switches 32 ₁-32 _(B), where N is the number of input/output ports of each photonic burst switch. Thus, in this embodiment, the maximum number of wavelengths at each photonic burst switch is A·C, where N>A·C+1. For embodiments in which N is greater than A·C, the extra input/output ports can be used to loop back an optical signal for buffering.

[0044] Further, although photonic burst switches 32 ₁-32 _(B) are shown as separate units, they can be implemented as N×N photonic burst switches using any suitable switch architecture. Module 17 also includes a set of optical wavelength division multiplexers 34 ₁-34 _(A), a set of optical-to-electrical signal converters 36 (e.g., photo-detectors), a control unit 37, and a set of electrical-to-optical signal converters 38 (e.g., lasers). Control unit 37 may have one or more processors to execute software or firmware programs.

[0045] The elements of this embodiment of module 17 are interconnected as follows. Optical demultiplexers 30 ₁-30 _(A) are connected to a set of A input optical fibers that propagate input optical signals from other switching nodes of photonic burst switched network 10 (FIG. 10). The output leads of the optical demultiplexers are connected to the set of B core optical switches 32 ₁-32 _(B) and to optical signal converter 36. For example, optical demultiplexer 30, has B output leads connected to input leads of the photonic burst switches 32 ₁-32 _(B) (i.e., one output lead of optical demultiplexer 30, to one input lead of each photonic burst switch) and at least one output lead connected to optical signal converter 36.

[0046] The output leads of photonic burst switches 32 ₁-32 _(B) are connected to optical multiplexers 34 ₁-34 _(A). For example, photonic burst switch 32, has A output leads connected to input leads of optical multiplexers 34 ₁-34 _(A) (i.e., one output lead of photonic burst switch 32, to one input lead of each optical multiplexer). Each optical multiplexer also an input lead connected to an output lead of electrical-to-optical signal converter 38. Control unit 37 has an input lead or port connected to the output lead or port of optical-to-electrical signal converter 36. The output leads of control unit 37 are connected to the control leads of photonic burst switches 32 ₁-32 _(B) and electrical-to-optical signal converter 38. As described below in conjunction with the flow diagram of FIG. 5, module 17 is used to receive and transmit optical control bursts, optical data bursts, and network management control bursts. In one embodiment, the optical data bursts and optical control bursts have transmission formats as shown in FIGS. 4A and 4B.

[0047]FIG. 4A illustrates the format of an optical data burst for use in PBS network 10 (FIG. 1), according to one embodiment of the present invention. In this embodiment, each optical data burst has a start guard band 40, an IP payload data segment 41, an IP header segment 42, a payload sync segment 43 (typically a small number of bits), and an end guard band 44 as shown in FIG. 4A. In some embodiments, IP payload data segment 41 includes the statistically multiplexed IP data packets or Ethernet frames used to form the burst. Although FIG. 4A shows the payload as contiguous, module 17 transmits payloads in a TDM format. Further, in some embodiments the data burst can be segmented over multiple TDM channels. It should be pointed out that in this embodiment the optical data bursts and optical control bursts have local significance only in PBS network 10, and may loose their significance at the optical WAN.

[0048]FIG. 4B illustrates the format of an optical control burst for use in photonic burst switched network 10 (FIG. 1), according to one embodiment of the present invention. In this embodiment, each optical control burst has a start guard band 46, an IP label data segment 47, a label sync segment 48 (typically a small number of bits), and an end guard band 49 as shown in FIG. 4B. In this embodiment, label data segment 45 includes all the necessary routing and timing information of the IP packets to form the optical burst. Although FIG. 4B shows the payload as contiguous, in this embodiment module 17 transmits labels in a TDM format.

[0049] In some embodiments, an optical network management control label (not shown) is also used in PBS network 10 (FIG. 1). In such embodiments, each optical network management control burst includes: a start guard band similar to start guard band 46; a network management data segment similar to data segment 47; a network management sync segment (typically a small number of bits) similar to label sync segment 48; and an end guard band similar to end guard band 44. In this embodiment, network management data segment includes network management information needed to coordinate transmissions over the network. In some embodiments, the optical network management control burst is transmitted in a TDM format.

[0050]FIG. 5 illustrates the operational flow of module 17 (FIG. 3), according to one embodiment of the present invention. Referring to FIGS. 3 and 5, module 17 operates as follows.

[0051] Module 17 receives an optical signal with TDM label and data signals. In this embodiment, module 17 receives an optical control signal (e.g., an optical control burst) and an optical data signal (i.e., an optical data burst in this embodiment) at one or two of the optical demultiplexers. For example, the optical control signal may be modulated on a first wavelength of an optical signal received by optical demultiplexer 30 _(A), while the optical data signal is modulated on a second wavelength of the optical signal received by optical demultiplexer 30 _(A). In some embodiments, the optical control signal may be received by a first optical demultiplexer while the optical data signal is received by a second optical demultiplexer. Further, in some cases, only an optical control signal (e.g., a network management control burst) is received. A block 51 represents this operation.

[0052] Module 17 converts the optical control signal into an electrical signal. In this embodiment, the optical control signal is the optical control burst signal, which is separated from the received optical data signal by the optical demultiplexer and sent to optical-to-electrical signal converter 36. In other embodiments, the optical control signal can be a network management control burst (previously described in conjunction with FIG. 4B). Optical-to-electrical signal converter 36 converts the optical control signal into an electrical signal. For example, in one embodiment each portion of the TDM control signal is converted to an electrical signal. The electrical control signals received by control unit 37 are processed to form a new control signal. In this embodiment, control unit 37 stores and processes the information included in the control signals. A block 53 represents this operation.

[0053] Module 17 then routes the optical data signals (i.e., optical data burst in this embodiment) to one of optical multiplexers 34 ₁-34 _(A), based on routing information included in the control signal. In this embodiment, control unit 37 processes the control burst to extract the routing and timing information and sends appropriate PBS configuration signals to the set of B photonic burst switches 32 ₁-32 _(B) to re-configure each of the photonic burst switches to switch the corresponding optical data bursts. A block 55 represents this operation.

[0054] Module 17 then converts the processed electrical control signal to a new optical control burst. In this embodiment, control unit 37 provides TDM channel alignment so that reconverted or new optical control bursts are generated in the desired wavelength and TDM time slot pattern. The new control burst may be modulated on a wavelength and/or time slot different from the wavelength and/or time slot of the control burst received in block 51. A block 57 represents this operation.

[0055] Module 17 then sends the optical control burst to the next switching node in the route. In this embodiment, electrical-to-optical signal generator 38 sends the new optical control burst to appropriate optical multiplexer of optical multiplexers 34 ₁-34 _(A) to achieve the route. A block 59 represents this operation.

[0056]FIG. 6 illustrates a GMPLS-based architecture for a PBS network, according to one embodiment of the present invention. Starting with the GMPLS suite of protocols, each of the GMPLS protocols can be modified or extended to support PBS operations and optical interfaces while still incorporating the GMPLS protocols' various traffic-engineering tasks. The integrated PBS layer architecture include PBS data services layer 60 on top of a PBS MAC layer 61, which is on top of a PBS photonics layer 62. It is well known that the GMPLS suite (indicated by a block 63 in FIG. 6) includes a provisioning component 64, a signaling component 65, a routing component 66, a label management component 67, a link management component 68, and a protection and restoration component 69. In some embodiments, these components are modified or have added extensions that support the PBS layers 60-62. Further, in this embodiment, GMPLS suite 63 is also extended to include an operation, administration, management and provisioning (OAM&P) component 70.

[0057] For example, signaling component 65 can include extensions specific to PBS networks such as, for example, burst start time, burst type, burst length, and burst priority, etc. Link management component 68 can be implemented based on the well-known link management protocol (LMP) (that currently supports only SONET/SDH networks) with the necessary extensions added to support PBS networks. For example, protection and restoration component 69 can be modified to cover PBS networks by one of ordinary skill in the art in light of the present disclosure.

[0058] Further, for example, label management component 67 can be modified to support a PBS control channel label space. In one embodiment, the label operations are performed after control channel signals are O-E converted. The ingress nodes of the PBS network act as label edge routers (LERs) while the switching nodes act as label switch routers (LSRs). An egress node acts as an egress LER substantially continuously providing all of the labels of the PBS network. Component 67 can advantageously help increase the speed of control channel context retrieval (by performing a pre-established label look-up instead of having to recover a full context).

[0059]FIG. 7 illustrates PBS optical burst flow between nodes in an exemplary PBS network 700, according to one embodiment of the present invention. System 700 includes ingress node 710, a switching node 712, an egress node 714 and other nodes (egress, switching, and ingress that are not shown to avoid obscuring the description of the optical burst flow). In this embodiment, the illustrated components of ingress, switching and egress nodes 710, 712 and 714 are implemented using machine-readable instructions that cause a machine (e.g., a processor) to perform operations that allow the nodes to transfer information to and from other nodes in the PBS network. In this example, the lightpath for the optical burst flow is from ingress node 710, to switching node 712 and then to egress node 714.

[0060] Ingress node 710 includes an ingress PBS MAC layer component 720 having a data burst assembler 721, a data burst scheduler 722, an offset time manager 724, a control burst builder 726 and a burst framer 728. In one embodiment, data burst assembler 721 assembles the data bursts to be optically transmitted over PBS network 10 (FIG. 1). In one embodiment, the size of the data burst is determined based on many different network parameters such as quality-of-service (QoS), number of available optical channels, the size of electronic buffering at the ingress nodes, the specific burst assembly algorithm, etc.

[0061] Data burst scheduler 722, in this embodiment, schedules the data burst transmission over PBS network 10 (FIG. 1). In this embodiment, ingress PBS MAC layer component 710 generates a bandwidth request for insertion into the control burst associated with the data burst being formed. In one embodiment, data burst scheduler 722 also generates the schedule to include an offset time (from offset time manager 724 described below) to allow for the various nodes in PBS network 10 to process the control burst before the associated data burst arrives.

[0062] In one embodiment, offset time manager 724 determines the offset time based on various network parameters such as, for example, the number of hops along the selected lightpath, the processing delay at each switching node, traffic loads for specific lightpaths, and class of service requirements.

[0063] Then control burst builder 726, in this embodiment, builds the control burst using information such as the requested bandwidth, burst scheduling time, in-band or OOB (defined above in conjunction with FIG. 1) signaling, burst destination address, data burst length, data burst channel wavelength, offset time, priorities, and the like.

[0064] Burst framer 728 frames the control and data bursts (using the framing format described below in conjunction with FIGS. 7-11 in some embodiments). Burst framer 728 then transmits the control burst over PBS network 10 via a physical optical interface (not shown), as indicated by an arrow 750. In this embodiment, the control burst is transmitted OOB to switching node 712, as indicated by an optical control burst 756 and PBS TDM channel 757 in FIG. 7. Burst framer 728 then transmits the data burst according to the schedule generated by burst scheduler 722 to switching node 712 over the PBS network via the physical optical interface, as indicated by an optical burst 758 and PBS TDM channel 759 in FIG. 7. The time delay between optical bursts 756 (control burst) and 758 (data burst) in indicated as an OFFSET, in FIG. 7.

[0065] Switching node 712 includes a PBS switch controller 730 that has a control burst processing component 732, a burst framer/de-framer 734 and a hardware PBS switch (not shown).

[0066] In this example, optical control burst 756 is received via a physical optical interface (not shown) and optical switch (not shown) and converted to electrical signals (i.e., O-E conversion). Control burst framer/de-framer 734 de-frames the control burst information and provides the control information to control burst processing component 732. Control burst processing component 732 processes the information, determining the corresponding data burst's destination, bandwidth reservation, next control hop, control label swapping, etc.

[0067] PBS switch controller component 730 uses some of this information to control and configure the optical switch (not shown) to switch the optical data burst at the appropriate time duration to the next node (i.e., egress node 714 in this example) at the proper channel. In some embodiments, if the reserved bandwidth is not available, PBS switch controller component 730 can take appropriate action. For example, in one embodiment PBS switch controller 730 can: (a) determine a different lightpath to avoid the unavailable optical channel (e.g., deflection routing); (b) delay the data bursts using integrated buffering elements within the PBS switch fabric such as fiber delay lines; (c) use a different optical channel (e.g. by using tunable wavelength converters); and/or (d) drop only the coetaneous data bursts. Some embodiments of PBS switch controller component 730 may also send a negative acknowledgment message back to ingress node 710 to re-transmit the dropped burst.

[0068] However, if the bandwidth can be found and reserved for the data burst, PBS switch controller component 730 provides appropriate control of the hardware PBS switch (not shown). In addition, PBS switch controller component 730 generates a new control burst based on the updated reserved bandwidth from control burst processing component 732 and the available PBS network resources. Control burst framer/de-framer 734 then frames the re-built control burst, which is then optically transmitted to egress node 714 via the physical optical interface (not shown) and the optical switch (not shown), as indicated by PBS TDM channel 764 and an optical control burst 766 in FIG. 7.

[0069] Subsequently, when the optical data burst corresponding to the received/processed control burst is received by switching node 712, the PBS switch fabric is already configured to switch the optical data burst and route it to egress node 714. In other situations, switching node 712 can switch the optical data burst to a different node (e.g., another switching node not shown in FIG. 7). The optical data burst from ingress node 710 is then switched to egress node 714, as indicated by PBS TDM channel 767 and an optical data burst 758A. In this embodiment, optical data burst 758A is simply optical data burst 758 re-routed by the hardware PBS switch (not shown), but possibly transmitted in a different TDM channel. The time delay between optical control burst 766 and optical data burst 758A is indicated by an OFFSET₂ in FIG. 7, which is smaller than OFFSET₁ due, for example, to processing delay and other timing errors in switching node 712.

[0070] Egress node 714 includes a PBS MAC component 740 that has a data demultiplexer 742, a data burst re-assembler 744, a control burst processing component 746, and a data burst de-framer 748.

[0071] Egress node 714 receives the optical control burst as indicated by an arrow 770 in FIG. 7. Burst de-framer 748 receives and de-frames the control burst via a physical O-E interface (not shown). In this embodiment, control burst processing component 746 processes the de-framed control burst to extract the pertinent control/address information.

[0072] After the control burst is received, egress node 714 receives the data burst(s) corresponding to the received control burst, as indicated by an arrow 772 in FIG. 7. In this example, egress node 714 receives the optical data burst after a delay of OFFSET₂, relative to the end of the control burst. In a manner similar to that described above for received control bursts, burst de-framer 748 receives and de-frames the data burst. Data burst re-assembler 744 then processes the de-framed data burst to extract the data (and to re-assemble the data if the data burst was a fragmented data burst). Data de-multiplexer 742 then appropriately de-multiplexes the extracted data for transmission to the appropriate destination (which can be a network other than the PBS network).

[0073]FIG. 8 illustrates a generic PBS framing format 800 for PBS optical bursts, according to one embodiment of the present invention. Generic PBS frame 800 includes a PBS generic burst header 802 and a PBS burst payload 804 (which can be either a control burst or a data burst). FIG. 8 also includes an expanded view of PBS generic burst header 802 and PBS burst payload 804.

[0074] PBS generic burst header 802 is common for all types of PBS bursts and includes a version number (VN) field 810, a payload type (PT) field 812, a control priority (CP) field 814, an in-band signaling (IB) field 816, a label present (LP) field 818, a header error correction (HEC) present (HP) field 819, a burst length field 822, and a burst ID field 824. In some embodiments, PBS generic burst header also includes a reserved field 820 and a HEC field 826. Specific field sizes and definitions are described below for framing format having 32-bit words; however, in other embodiments, the sizes, order and definitions can be different.

[0075] In this embodiment, PBS generic burst header 802 is a 4-word header. The first header word includes VN field 810, PT field 812, CP field 814, IB field 816 and LP field 818. VN field 810 in this exemplary embodiment is a 4-bit field (e.g., bits 0-3) defining the version number of the PBS Framing format being used to frame the PBS burst. In this embodiment, VN field 810 is defined as the first 4-bits of the first word, but in other embodiments, it need not be the first 4-bits, in the first word, or limited to 4-bits.

[0076] PT field 812 is a 4-bit field (bits 4-7) that defines the payload type. For example, binary “0000” may indicate that the PBS burst is a data burst, while binary “0001” indicates that the PBS burst is a control burst, and binary “0010” indicates that the PBS burst is a management burst. In this embodiment, PT field 812 is defined as the second 4-bits of the first word, but in other embodiments, it need not be the second 4-bits, in the first word, or limited to 4-bits.

[0077] CP field 814 is a 2-bit field (bits 8-9) that defines the burst's priority. For example, binary “00” may indicate a normal priority while binary “01” indicates a high priority. In this embodiment, CP field 814 is defined bits 8 and 9 of the first word, but in other embodiments, it need not be bits 8 and 9, in the first word, or limited to 2-bits.

[0078] IB field 816 is a one-bit field (bit 10) that indicates whether the PBS control burst is being signaled in-band or OOB. For example, binary “0” may indicate OOB signaling while binary “1” indicates in-band signaling. In this embodiment, IB field 816 is defined as bit 10 of the first word, but in other embodiments, it need not be bit 10, in the first word, or limited to one-bit.

[0079] LP field 818 is a one-bit field (bit 11) used to indicate whether a label has been established for the lightpath carrying this header. In this embodiment, LP field 818 is defined as bit 11 of the first word, but in other embodiments, it need not be bit 11, in the first word, or limited to one-bit.

[0080] HP field 819 is a one-bit field (bit 12) used to indicate whether header error correction is being used in this control burst. In this embodiment, HP field 819 is defined as bit 12 of the first word, but in other embodiments, it need not be bit 12, in the first word, or limited to one-bit. The unused bits (bits 13-31) form field(s) 820 that are currently unused and reserved for future use.

[0081] The second word in PBS generic burst header 802, in this embodiment, includes PBS burst length field 822, which is used to store a binary value equal to the length of the number of bytes in PBS burst payload 804. In this embodiment, the PBS burst length field is 32-bits. In other embodiments, PBS burst length field 822 need not be in the second word and is not limited to 32-bits.

[0082] In this embodiment, the third word in PBS generic burst header 802 includes PBS burst ID field 824, which is used to store an identification number for this burst. In this embodiment, PBS burst ID field 824 is 32-bits generated by the ingress node (e.g., ingress node 710 in FIG. 7). In other embodiments, PBS burst ID field 824 need not be in the third word and is not limited to 32-bits.

[0083] The fourth word in PBS generic burst header 802, in this embodiment, includes generic burst header HEC field 826, which is used to store an error correction word. In this embodiment, generic burst header HEC field 826 is 32-bits generated using any suitable known error correction technique. In other embodiments, generic burst header HEC field 826 need not be in the fourth word and is not limited to 32-bits. As in indicated in FIG. 8, generic burst header HEC field 826 is optional in that if error correction is not used, the field may be filled with all zeros. In other embodiments, generic burst header HEC field 826 is not included in PBS generic burst header 802.

[0084] PBS burst payload 804 is common for all types of PBS bursts and includes a PBS specific payload header field 832, a payload field 834, and a payload frame check sequence (FCS) field 836.

[0085] In this exemplary embodiment, PBS specific payload header 832 is the first part (i.e., one or more words) of PBS burst payload 804. Typically, specific payload header field 832 includes one or more fields for information related to a data burst, which can be either this burst itself or included in another burst associated with this burst (i.e., when this burst is a control burst).

[0086] Payload data field 834, in this embodiment, is the next portion of PBS burst payload 804. In some embodiments, control bursts have no payload data, so this field may be omitted or include all zeros. For data bursts, payload data field 834 may be relatively large (e.g., including multiple IP packets or Ethernet frames).

[0087] Payload FCS field 836, in this embodiment, in the next portion of PBS burst payload. In this embodiment, payload FCS field 836 is a one-word field (i.e., 32-bits) used in error detection and/or correction. As in indicated in FIG. 8, payload FCS field 836 is optional in that if error detection/correction is not used, the field may be filled with all zeros. In other embodiments, payload FCS field 836 is not included in PBS burst payload 804.

[0088]FIG. 9 illustrates a block diagram of an edge node 900 with adaptive monitoring for use in a PBS network, according to one embodiment of the present invention. In this embodiment, edge node 900 includes an ingress PBS MAC component 720A and an egress PBS MAC component 740A. In another embodiment, adaptive ingress PBS component 720A is present without the adaptive egress PBS component 740A and vice-versa in order to achieve the throughput improvement.

[0089] Ingress PBS MAC component 720A contains several elements that perform operations similar to like-numbered elements discussed above with reference to FIG. 7. These include a data burst assembler 721, a burst scheduler 722, and offset manager 724, a control burst builder 726, and a burst framer 728. Similarly, egress PBS MAC component 740A includes elements that that perform operations similar to like-numbered elements discussed above with reference to FIG. 7, including an optical de-multiplexer 742, a data burst re-assembler 744, a control burst processor 746, and a burst de-framer 748. In addition to the new adaptive PBS monitoring layers, ingress PBS MAC component 720A includes a “deep” packet inspector 906 and PBS data/control queues 908, while egress PBS MAC component 740A includes a “deep” packet inspector 910 and PBS data/control queues 912.

[0090] In operation, the PBS network that includes edge node 900 may experience traffic contention when transmitting PBS data bursts from edge node 900 to another edge node, which can result in one or more PBS data bursts being dropped. The dropped PBS data burst(s) will typically include segments from multiple flows because edge node 900 in default operation performs statistical multiplexing in forming the PBS data burst(s). To handle dropped packets, some transport layer protocols (e.g., transport control protocol or TCP) have recovery and retransmit mechanisms (e.g., TCP Slow Start and Congestion Avoidance for the TCP/IP protocol (ETF TCP Specification: http://www.ietf.org/rfc/rfc0793.txt). When PBS data burst(s) are dropped at an edge node, the recovery and retransmit mechanisms can cause the source (i.e., edge node 900 in this example) to initiate recovery and retransmit operations for each flow that experienced lost frames. However, in accordance with embodiments of the present invention, ingress and egress adaptive monitors 902 and 904 provide added flexibility in building PBS data bursts so that the recovery and retransmit mechanisms can be performed more efficiently with respect to PBS network throughput. The operation of ingress and egress adaptive monitors 902 and 904 are described below in conjunction with FIGS. 10 and 11, respectively. Although this embodiment of edge node 900 has both ingress and egress adaptive monitors 902 and 904, in other embodiments the edge node may have only one of these adaptive monitors, as discussed above.

[0091]FIG. 10 illustrates the operation of edge node 900 (FIG. 9) during ingress adaptive monitoring, according to one embodiment of the present invention. Referring to FIGS. 9 and 10, this embodiment of edge node 900 performs ingress adaptive monitoring as follows. Edge node 900 receives data to be transmitted to one or more destinations via the PBS network (PBSN) of which edge node 900 is a part. In one embodiment, the data is received from source(s) external to the PBS network in packets according to the TCP/IP protocol to be transmitted to destination(s) coupled to an egress edge node of the PBSN. In other embodiments, the incoming data can be in packets/frames according to different protocols. A block 1001 represents this operation.

[0092] In this embodiment, ingress adaptive monitor 902 then determines if a TCP slow start is needed or being continued. TCP slow start is a congestion relief feature of the TCP/IP protocol in which the number of segments in a packet is increased slowly after having been exponentially decreased in response to dropped segments. In particular, the number of segments is increased by one until a predetermined maximum number is reached as defined in TCP by the optimal window size, each time a packet is acknowledged. In addition, TCP slow start is also used when starting a TCP flow. A block 1003 represents this operation. In one embodiment, the TCP protocol or state machine is not modified, but instead it monitors or uses information provided from the TCP stack, e.g. “performing slow start”.

[0093] If a TCP slow start is needed/continued, ingress adaptive monitor 902 causes data burst assembler 721 of edge node 900 to form a PBS data burst as follows. If the TCP flow is just starting, the PBS data burst size is adjusted to only accommodate one segment of the TCP flow. If a TCP slow start has already been initiated, TCP increases the number of segments to transmit and the PBS data burst size is increased to match the size needed to transfer these segments. Note the number of segments for the TCP flow in a PBS data burst has a maximum window size given by the TCP flow's destination. A block 1005 represents this operation. This adaptation of the PBS burst size to the TCP flow size allows the PBS data burst to be transmitted immediately upon receiving the specified number of segments for the TCP flow experiencing the TCP slow start, rather than waiting for the PBS burst to be filled with segments from other TCP flows or waiting for the transmission time-out to expire. In another embodiment, even at run time the PBS burst size is adapted to the size required by the number of TCP segment, up to the maximum PBS burst size.

[0094] If adaptive monitoring is turned on in edge node 900 (i.e., ingress adaptive monitor 902 is enabled), ingress adaptive monitor 902 then determines whether the number of dropped segments exceeds a preselected threshold (e.g., set up by an external policy). For example, the preselected threshold may be the average number of dropped packets that occurred during a preselected time window. Blocks 1007 and 1009 represent this operational flow. In one embodiment, ingress adaptive monitor 902 performs (via deep packet inspector 906) a “deep” packet inspection of control packets coming back to the data source (via edge node 900) from the destination PBSN edge node to detect packet losses. For example, deep packet inspector 906 may check for unacknowledged packets, which can occur when the PBS data burst(s) containing the packets are dropped.

[0095] If the losses do not exceed the preselected threshold, data burst assembler 721 of edge node 900 builds the PBS data bursts using the default framing procedure (including TCP slow start requirements, if any). A block 1011 represents this operation. In addition, if adaptive monitoring is not turned on (see block 1007), the operational flow proceeds to block 1011. However, if in block 1009 the losses exceed the preselected threshold, ingress adaptive monitor 902 then causes data burst assembler 721 to build PBS data burst(s) using an alternative framing procedure. A block 1013 represents this operation.

[0096] In this embodiment, the alternative framing procedure provides artificial correction of the segments in the PBS data burst(s). In one embodiment, ingress adaptive monitor 902 causes data burst assembler 721 to stop statistically multiplexing the incoming data, and instead create PBS data burst(s) that each contain only segments from a single flow. Because the resulting PBS data burst(s) each have segments from only one flow, when a PBS data burst is lost, only segments from a single flow are lost rather than from multiple flows. Consequently, the egress edge node of the PBSN will avoid having to send a series of retransmit requests back to the source for the various flows for the missing segments (as would be the case with statistically multiplexed PBS data bursts). Instead, because all of the segments are lost when PBS data bursts are artificially correlated, the TCP retransmission time-out (RTO) mechanism will be triggered. Artificially-correlated PBS data bursts are believed to achieve better throughput than statistically multiplexed PBS data bursts under lossy conditions. The threshold of block 1009 can be set to a level at which artificially correlated PBS data bursts have better throughput than statistically multiplexed PBS data bursts. In other embodiments, other framing procedures can be used to increase throughput when PBS data bursts are dropped. For example, based on threshold values, the alternative framing procedure can be to send redundant or interleaved flow in the PBS data burst(s) or use a back-off algorithm to calculate the PBS window size in order to provide a more reliable transport network.

[0097] The foregoing operations may be implemented by a “back-off” algorithm for PBS data burst size adaptation in instances in which data burst losses are encountered. For example, a back-off algorithm may be used in an Ethernet network for contention resolution. In one embodiment an exponential back-off algorithm is employed, which operates in the following manner. Collisions arise when two nodes try to send their frames. These collisions are monitored, and in response the transmitting nodes stop transmission of their frames. After a frame collision, a transmitting node aborts the remainder of its frame wait for a random period of time. Computation of the exponential back-off time at the j'th trial (after j-1) collisions) random variable r is chosen as follows:

0<=r<2 min(j,10)

[0098] If two frames collides, and two nodes choose different r's, the contention resolves.

[0099] Following the performance of blocks 1011 and 1013, the resulting PBS data burst(s) are then scheduled and transmitted. In this embodiment, burst scheduler 722, offset manager 724 and burst framer 728 schedules and transmits these PBS data burst(s). A block 1015 represents this operation. The operational flow then returns to block 1001 to process more data for transmission through the PBSN.

[0100]FIG. 11 illustrates the operation of edge node 900 (FIG. 9) during egress adaptive monitoring, according to one embodiment of the present invention. Referring to FIGS. 9 and 11, this embodiment of edge node 900 performs egress adaptive monitoring as follows. From a node of the PBSN, edge node 900 receives PBS data burst(s) containing data to be transmitted to one or more destinations (external to the PBSN) coupled to edge node 900. In one embodiment, the data is to be transmitted to the destination(s) in packets according to the TCP/IP protocol. In other embodiments, the data can be transmitted in packets/frames according to different protocols. A block 1101 represents this operation.

[0101] If adaptive monitoring is turned on in edge node 900 (i.e., egress adaptive monitor 904 is enabled), egress adaptive monitor 904 then determines whether the number of dropped segments exceeds a preselected threshold (e.g., set up by an external policy). This threshold can be the same as in block 1009 (FIG. 10) in some embodiments. Blocks 1103 and 1105 represent this operational flow. In one embodiment, egress adaptive monitor 904 monitors the number of retransmission requests to detect PBS control/data bursts' losses.

[0102] If the losses do not exceed the preselected threshold, edge node 900 continues to send retransmission requests for dropped segments according to the TCP/IP protocol. A block 1107 represents this operation. In addition, if adaptive monitoring is not turned on (see block 1103), the operational flow proceeds to block 1107. However, if in block 1105 the losses exceed the preselected threshold, egress adaptive monitor 904 then employs an alternative framing procedure to reduce losses, wherein the ACK packets are adjusted to either be artificially correlated, interleaved, etc. This is to also guarantee that since there are losses on the network, the egress will do its best to guarantee that the control packets get back to the ingress. A block 1109 represents this operation. In one embodiment, the alternative framing procedure is to build the previously described artificially correlated PBS data bursts. In other embodiments, the alternative framing procedure can be the send redundant and interleaved in the PBS data burst(s). The operational flow then proceeds to a block 1111 in which burst(s) are scheduled and transmitted in a manner similar to that discussed above with reference to block 1015 in FIG. 10. The operational flow then returns to block 1101 to process more data (i.e. data in PBS data bursts) received from the PBSN for transmission to the external destination(s).

[0103] Embodiments of architectures, methods and apparatus for implementing a PBS network are described herein. In the above description, numerous specific details are set forth to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that embodiments of the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring this description.

[0104] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable optical manner in one or more embodiments.

[0105] Thus, embodiments of this invention may be used as or to support software program executed upon some form of processing core (such as the CPU of a computer or a processor of a module) or otherwise implemented or realized upon or within a machine-readable medium. A machine-readable medium includes any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, a machine-readable medium can include such as a read only memory (ROM); a random access memory (RAM); a magnetic disk storage media; an optical storage media; and a flash memory device, etc. In addition, a machine-readable medium can include propagated signals such as electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.).

[0106] In the foregoing specification, embodiments of the invention have been described. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. 

1. A system comprising: a burst assembler to form data bursts from data received from a data source to be transmitted over an optical network; and an adaptive monitor to selectively cause the burst assembler to form statistically multiplexed data bursts in response to detecting that losses incurred in previous transmissions of data over the optical network fall into a first preselected category and to selectively cause the burst assembler to form data bursts according to another format in response to detecting that losses incurred in previous transmissions of data over the optical network fall into a second preselected category.
 2. The system of claim 1 wherein the system is to selectively form a control burst corresponding to a data burst formed by the burst assembler, the control burst to selectively configure optical switches of selected optical switching nodes in the optical network before the system transmits the corresponding data burst over the optical network.
 3. The system of claim 1 wherein the first preselected category includes transmission losses that have an average that is below a preselected threshold.
 4. The system of claim 1 wherein the second preselected category includes transmission losses that have an average that is above a preselected threshold.
 5. The system of claim 1 wherein the optical network comprises a wavelength division multiplexed (WDM) network.
 6. The system of claim 1 wherein the adaptive monitor is to selectively cause the burst assembler to form data bursts that each have data from a single flow in response to detecting that losses incurred in previous transmissions of data over the optical network fall into the second preselected category.
 7. The system of claim 1 wherein the adaptive monitor is to selectively cause the burst assembler to form data bursts that each have less data than previously transmitted data bursts that were lost during transmission in response to detecting that losses incurred in previous transmissions of data over the optical network fall into the second preselected category.
 8. The system of claim 1 wherein the adaptive monitor is to detect losses by tracking acknowledgment messages corresponding to data in previously transmitted data bursts.
 9. The system of claim 1 wherein the adaptive monitor is to detect losses by tracking retransmit messages corresponding to data in previously transmitted data bursts.
 10. The system of claim 1 wherein the adaptive monitor is to selectively cause the burst assembler to complete formation of a data burst in response to adding a predetermined amount of data from a newly started flow to the statistically multiplexed data burst, the predetermined amount of data being less than the statistically multiplexed data burst's maximum capacity.
 11. A method comprising: receiving data from a data source to be transmitted to a destination via an optical network; selectively forming a data burst from the received data according to a statistically multiplexed format in response to detecting that losses incurred in previous transmissions of data over the optical network fall into a first preselected category; and selectively forming a data burst according to another format in response to detecting that losses incurred in previous transmissions of data over the optical network fall into a second preselected category.
 12. The method of claim 11 further comprising selectively forming a control burst corresponding to a previously formed data burst, the control burst to selectively configure optical switches of selected optical switching nodes in the optical network before the corresponding data burst is transmitted over the optical network.
 13. The method of claim 11 wherein the first preselected category includes transmission losses that have an average that is below a preselected threshold.
 14. The method of claim 11 wherein the second preselected category includes transmission losses that have an average that is above a preselected threshold.
 15. The method of claim 11 wherein the optical network comprises a wavelength division multiplexed (WDM) network.
 16. The method of claim 11 wherein selectively forming a data burst according to another format comprises forming a data burst with data from only a single flow.
 17. The method of claim 11 wherein selectively forming a data burst according to another format comprises forming the data burst to have less data than previously transmitted data bursts that were lost during transmission.
 18. The method of claim 11 further comprising detecting losses in previously transmitted data bursts by tracking acknowledgment messages corresponding to data in the previously transmitted data bursts.
 19. The method of claim 11 further comprising detecting losses in previously transmitted data bursts by tracking retransmit messages corresponding to data in previously transmitted data bursts.
 20. The method of claim 11 further comprising completing formation of a data burst in response to adding a predetermined amount of data from a newly started flow to the data burst, the predetermined amount of data being less than the data burst's maximum capacity.
 21. An optical network, comprising: a plurality of optical switching nodes; first and second edge nodes coupled to the plurality of optical switching nodes, wherein the first edge node comprises: a burst assembler to form data bursts from data received from a data source to be transmitted over the optical network; and an adaptive monitor to selectively cause the burst assembler to form statistically multiplexed data bursts in response to detecting that losses incurred in previous transmissions of data over the optical network fall into a first preselected category and to selectively cause the burst assembler to form data bursts according to another format in response to detecting that losses incurred in previous transmissions of data over the optical network fall into a second preselected category.
 22. The optical network of claim 21 wherein the first edge node is to selectively form a control burst corresponding to a data burst formed by the burst assembler, the control burst to selectively configure an optical switch of a selected optical switching node of the plurality of optical switches before the system transmits the corresponding data burst over the optical network.
 23. The optical network of claim 21 wherein the first preselected category includes transmission losses that have an average that is below a preselected threshold.
 24. The optical network of claim 21 wherein the second preselected category includes transmission losses that have an average that is above a preselected threshold.
 25. The optical network of claim 21 wherein the optical network comprises a wavelength division multiplexed (WDM) network.
 26. The optical network of claim 21 wherein the adaptive monitor is to selectively cause the burst assembler to form data bursts that each have data from a single flow in response to detecting that losses incurred in previous transmissions of data over the optical network fall into the second preselected category.
 27. The optical network of claim 21 wherein the adaptive monitor is to selectively cause the burst assembler to form data bursts that each have less data than previously transmitted data bursts that were lost during transmission in response to detecting that losses incurred in previous transmissions of data over the optical network fall into the second preselected category.
 28. The optical network of claim 21 wherein the adaptive monitor is to detect losses by tracking acknowledgment messages corresponding to data in previously transmitted data bursts.
 29. The optical network of claim 21 wherein the adaptive monitor is to detect losses by tracking retransmit messages corresponding to data in previously transmitted data bursts.
 30. The optical network of claim 21 wherein the adaptive monitor is to selectively cause the burst assembler to prevent addition of data to a statistically multiplexed data burst in response to adding a predetermined amount of data from a newly started flow to the statistically multiplexed data burst, the predetermined amount of data being less than the statistically multiplexed data burst's maximum capacity for the newly started flow.
 31. A system comprising: a data burst demultiplexer to selectively send data extracted from a data burst to a destination coupled to the system in response to receiving the data burst from an edge node of an optical network; and an adaptive monitor to selectively cause the system to send a request to the edge node to form data bursts according to a second format in response to detecting that losses incurred in previous transmissions from the edge node of data bursts according to a first format fall into a preselected category.
 32. The system of claim 31 wherein the first format includes having statistically multiplexed data in the data burst.
 33. The system of claim 31 wherein the second format includes having non-statistically multiplexed data in the data burst.
 34. The system of claim 31 wherein the preselected category includes transmission losses that have an average that is above a preselected threshold.
 35. The system of claim 31 wherein the optical network comprises a wavelength division multiplexed (WDM) network.
 36. The system of claim 31 wherein a data burst according to the second format has data from only a single flow.
 37. The system of claim 31 wherein a data burst according to the second format has a smaller data capacity than a data burst according to the first format.
 38. The system of claim 31 wherein the adaptive monitor is to detect losses by tracking acknowledgment messages corresponding to data in previously transmitted data bursts.
 39. The system of claim 31 wherein the adaptive monitor is to detect losses by tracking retransmit messages corresponding to data in previously transmitted data bursts.
 40. The system of claim 31 wherein the request is included in a data burst sent by the system to the edge node.
 41. A method comprising: selectively sending data extracted from a data burst to a destination coupled to a first edge node of an optical network in response to receiving the data burst transmitted by a second edge node of the optical network; and selectively causing the second edge node to send a request to the first edge node to form data bursts according to a second format in response to detecting that losses incurred in previous transmissions from the edge node of data bursts according to a first format fall into a preselected category.
 42. The method of claim 41 wherein the first format includes having statistically multiplexed data in the data burst.
 43. The method of claim 41 wherein the second format includes having non-statistically multiplexed data in the data burst.
 44. The method of claim 41 wherein the preselected category includes transmission losses that have an average that is above a preselected threshold.
 45. The method of claim 41 wherein the optical network comprises a wavelength division multiplexed (WDM) network.
 46. The method of claim 41 wherein a data burst according to the second format has data from only a single flow.
 47. The method of claim 41 wherein a data burst according to the second format has a smaller data capacity than a data burst according to the first format.
 48. The method of claim 41 wherein detecting that losses incurred in previous transmissions further comprises tracking acknowledgment messages corresponding to data in previously transmitted data bursts.
 49. The method of claim 43441 wherein detecting that losses incurred in previous transmission further comprises tracking retransmit messages corresponding to data in previously transmitted data bursts.
 50. The method of claim 41 wherein the request is included in a data burst sent by the system to the edge node.
 51. An optical network, comprising: a plurality of optical switching nodes; first and second edge nodes coupled to the plurality of optical switching nodes, wherein the second edge node comprises: a data burst demultiplexer to selectively send data extracted from a data burst to a destination coupled to the optical network in response to receiving the data burst from the first edge node via the plurality of optical switching nodes; and an adaptive monitor to selectively cause the second edge node to send a request to the first edge node to form data bursts according to a second format in response to detecting that losses incurred in previous transmissions from the edge node of data bursts according to a first format fall into a preselected category. Describe 2^(nd) edge node:
 52. The optical network of claim 51 wherein the first format includes having statistically multiplexed data in the data burst.
 53. The optical network of claim 51 wherein the second format includes having non-statistically multiplexed data in the data burst.
 54. The optical network of claim 51 wherein the preselected category includes transmission losses that have an average that is above a preselected threshold.
 55. The optical network of claim 51 wherein the optical network comprises a wavelength division multiplexed (WDM) network.
 56. The optical network of claim 51 wherein a data burst according to the second format has data from only a single flow.
 57. The optical network of claim 51 wherein a data burst according to the second format has a smaller data capacity than a data burst according to the first format.
 58. The optical network of claim 51 wherein the adaptive monitor is to detect losses by tracking acknowledgment messages corresponding to data in previously transmitted data bursts.
 59. The optical network of claim 51 wherein the adaptive monitor is to detect losses by tracking retransmit messages corresponding to data in previously transmitted data bursts.
 60. The optical network of claim 51 wherein the request is included in a data burst sent by the system to the edge node. 